#!/usr/bin/env python3

import os
import sys
import time
import importlib
import signal

delay = 2

#
# In production, we've seen trackbacks like:
#
#  File "/home/pokybuild/yocto-worker/oe-selftest-fedora/build/meta/lib/oe/package_manager/__init__.py", line 17, in <module>:
#     import string
#    >from oe.gpg_sign import get_signer
#     import hashlib
#  File "<frozen importlib._bootstrap>", line 1004, in _find_and_load(name='oe.gpg_sign', import_=<built-in function __import__>)
#  File "<frozen importlib._bootstrap>", line 158, in _ModuleLockManager.__enter__()
#  File "<frozen importlib._bootstrap>", line 110, in _ModuleLock.acquire()
# KeyError: 139622474778432
# 
# and
#
#   File "/home/pokybuild/yocto-worker/oe-selftest-centos/build/meta/classes/base.bbclass", line 30, in oe_import(d=<bb.data_smart.DataSmart object at 0x7fba6a689760>):
#                 # Make a python object accessible from the metadata
#    >            bb.utils._context[toimport.split(".", 1)[0]] = __import__(toimport)
#             except AttributeError as e:
#  File "<frozen importlib._bootstrap>", line 1004, in _find_and_load(name='oe.path', import_=<built-in function __import__>)
#  File "<frozen importlib._bootstrap>", line 158, in _ModuleLockManager.__enter__()
#  File "<frozen importlib._bootstrap>", line 110, in _ModuleLock.acquire()
# KeyError: 140438942700992
#

#
# This reproduction script shows that if an import XXX is in progress and waiting at the wrong 
# point when an interrupt arrives (in this case a signal) and triggers it's own import YYY, 
# _blocking_on[tid] gets overwritten and lost, triggering the traceback we see above upon
# exit of the second import. I don't know what the interrupt is in our production case, I just
# use a signal handler here to prove it is possible.
#

implib = sys.modules["_frozen_importlib"]
_thread = sys.modules["_thread"]
_blocking_on = implib._blocking_on

# This is acquire from importlib/_bootstrap.py with a delay inserted between self being
# added to _blocking_on and obtaining the lock. It needs to match your python install
def acquire(self):
    global delay
    tid = _thread.get_ident()
    if tid in _blocking_on:
        print("TID already in blocking_on from %s but called by %s" % (_blocking_on[tid].name, self.name))
        delay = 0
    _blocking_on[tid] = self
    if delay:
        time.sleep(delay)
    try:
        while True:
            with self.lock:
                if self.count == 0 or self.owner == tid:
                    self.owner = tid
                    self.count += 1
                    return True
                if self.has_deadlock():
                    raise _DeadlockError('deadlock detected by %r' % self)
                if self.wakeup.acquire(False):
                    self.waiters += 1
            # Wait for a release() call
            self.wakeup.acquire()
            self.wakeup.release()
    finally:
        del _blocking_on[tid]

implib._ModuleLock.acquire = acquire

def handler(signum, frame):
    print("Handler starting import")
    delay = 0
    import glob
    print("Handler completed import")
    return

signal.signal(signal.SIGALRM, handler)
signal.alarm(1)

print("Process starting import")
import datetime
print("Process completed import")